Browsing by Author "Wang, Shu-Min"

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Ligands affect the crystal structure and photovoltaic performance of thin films of PbSe quantum dots
(2011)
Kuo, Chih-Yin
;
Su, Ming-Shin
;
Ku, Ching-Shun
;
Wang, Shu-Min
;
Lee, Hsin-Yi
We have prepared thin films of PbSe quantum dots (QDs) featuring three different ligands, oleic acid (OA), butylamine (BA), and 1,2-ethanedithiol (EDT), which have pronounced affects on the arrangement and photovoltaic performance of the PbSe QDs in the thin films. Transmission electron microscopy revealed that ligands that altered the inter-QD spacing induced significant changes in the packing of the PbSe QDs in localized regions of small areas (300 x 300 nm) of the thin films: from a superlattice of OA-capped PbSe QDs to a chaotic pattern of EDT-capped PbSe QDs. Using a synchrotron X-ray reflectivity probe and data fitting, we determined that the roughness decreased and the average densities increased for large-area (1.5 x 1.5 cm) PbSe QD thin films capped with BA and EDT, relative to those of the OA-capped PbSe QD film. In particular, the PbSe QDs' vertical packing density, which is critical for charge transport, increased substantially for the system incorporating EDT ligands. As a result, devices containing the EDT-treated PbSe QD film as the active layer displayed much improved power conversion efficiencies (PCEs) relative to those of corresponding devices featuring either the OA-or BA-capped PbSe QD films as active layers. Adopting a layer-by-layer technique, we fabricated a EDT-capped PbSe QD device that exhibited a PCE of 2.45%.
The dual localized surface plasmonic effects of gold nanodots and gold nanoparticles enhance the performance of bulk heterojunction polymer solar cells
(2013-10-01)
Liu, Chih-Ming
;
Chen, Chia-Min
;
Su, Yu-Wei
;
Wang, Shu-Min
;
Wei, Kung-Hwa
In this study, we investigated the effects of plasmonic resonances induced by gold nanodots (Au NDs), thermally deposited on the active layer, and octahedral gold nanoparticles (Au NPs), incorporated within the hole transport layer, on the performance of bulk heterojunction polymer solar cells (PSCs) based on poly(3-hexyl thiophene) (P3HT) and [ 6,6]-phenyl-C(61)butyric acid methyl ester (PC61BM). Thermal deposition of 5.3-nm Au NDs between the active layer and the cathode in a P3HT:PC61BM device resulted in the power conversion efficiency (PCE) of 4.6%-that is 15% greater than that (4.0%) for the P3HT:PC61BM device without Au NDs. The Au NDs provided near-field enhancement through excitation of the localized surface plasmon resonance (LSPR), thereby enhancing the degree of light absorption. In addition to the thermally deposited Au-NDs, embedding Au NPs within the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to form a dual metallic nanostructure can further enhance PCE to 4.8%-that is about 20% greater than that of the conventional P3HT:PC61BM cell. Thus, Au NPs and Au NDs appear to have great potential for the application in high-efficiency LSPR-enhanced PSCs. (C) 2013 Published by Elsevier B.V.